Process for converting gasoline of low antiknock rating into gasoline of high antiknock rating



C. 2,032,861 PROCESS FOR CONVERTING GAsoLlNE oF Low ANTIKNOCK March 3, 1936.

B. WATSON RATING INTO GASOLINE OF HIGH ANTIKNOCK RATING Filed Sep. 23, 1930 QWL :JM/vento@ Cornel i us'wntsn www Tm hr3@ Groom.,

WA 74W Patented Mar. 3, 1936 UNITED STATES PATENT OFFICE Cornelius B. Watson, Chicago, lll., assignor to The Pure Oil Company, Chicago, Ill., a corporation ol.' Ohio Application September 23, 1930, Serial No. 483,846

s claims.- (ci. 19e-sn y gasolines possessing a high anti-knock rating and This invention relates to an improved process for treating gasolines of low anti-knock rating,

especially those ofthe parafnn base type, ob-

tained from Pennsylvania and Michigan crudes, to increase the so-called anti-knock values of s uch gasolines to the end of rendering them more eflicient for use as fuels in modern internal combustion engines. Gasolines produced by usual reilning methods from Michigan and Pennsylvania crudes consist mainly of saturated hydrocarbons of the paraiin seriesand when used as fuels in internal combustion engines, the explosion characteristics thereof are such as to produce what is ordinarily known as detonation or knock, which characteristic increases directly with the compression ratio of such engines., Therefore, in the commercial use of such gasolines, the same are frequently blended with other. hydrocarbon oils containing high percentages of aromatic andl unsaturated hydrocarbons to produce a synthetic or composite fuel having a desired 4anti-knock rating. Again, foreign substances, such as tetraethyl lead, are often introduced into these gasolines to increaseto a desired degree their anti-4 knock values.

or unsaturated hydrocarbons. 'I'hese hydrocar bons are then subjected' to fractionation and condensation to obtain a motor fuel having the boiling range of gasoline but which possesses a much higher anti-knock value when used as a fuel for internal combustion engines than the low antiknock gasolines initially charged to the system. In the operation of oil reilneries, large quan, tities of gasoline of low anti-knock rating are being produced by distillation, topping or skimming operations and also with the use of certain types of cracking processes, although cracked gasolines generally possess a higher anti-knock rating than straight run gasolines. These gasolines are diflicult to dispose of proiltably for use as motor fuels due, principally, to their low anti-knock rating,I and it is therefore one of the outstanding objects of the present invention to' to thereby increase their economic value to the renner.

In the accompanying drawing, -there is illustrated diagrammatically apparatus employed in connection with the process comprising the present invention.

The numeral lI designates a supply tank containing gasoline of low anti-knock rating which i's adapted to be treated or processed in accordance with the present invention. This gasoline,

for example, may consist of straight run gasolines venience in description, the gasoline supplied to the tank l may be said to possessy a low antiknock rating when used as fuels for internalcombustion engines. Usually, these gasolines consist of hydrocarbons of the parafln and saturated type. l v

Leading from the tank I is a pipe line 2 in which is arranged a pump 3 by which the gasoline withdrawn from the tank I- may be passed through a reuxing coil 4 located in the upper portion of a fractionating tower 5. By forcing the gasoline. through the coil 4, the temperature of said gasoline is raised by indirect contact with the heated oil vapors passing upwardly through the tower 5 in order that by this operation there will be secured (a) vaporization of the lighter ends of the gasoline forced through the coil and (b) control of the end point of the vapors passing from the fractionating tower.

.After passing through the coil I, the heated gasolines which may possess a temperature, for example, of approximately 250 to 300". F., are delivered into a. separating tower 6 wherein the lighter ends ofthe gasoline, whichare in a vaporouscondition at the temperature specled,

pass overhead from the tower 6 through a line 1 and thence through a condenser 8 to a storage tank 9. By this method of operation, the lighter .ends of the gasoline are permanently removed from the system aheadof the cracking zone to avoid high permanent gas losses which would obtain by the cracking of these light ends into permanent gas.

The relatively high boiling point naphtha, which collects in the bottom of the separating tower 6, is removed by the pipe line I0 and forced by means of a pump Il through a pipe line Ila to the inlet side of a bank vof heating tubes I2 arranged in the outlet duct of a converting furnace I I. 'I'he temperature of the furnace gases passing through the duct Il is suiliciently high to eifect'vaporization of the greater proportion of the oils charged thereto but without any sub-- stantial cracking thereof. The oil or oil vapors discharged from the tubes I2 pass at a temperature of, for example, 650 F. to an evaporator Il arranged exteriorly of the converter and. which is usually unheated. From the bottom of .this evaporator high boiling liquid oils are removed through the line I 6, and are'permanently'dis'- charged from the system as a fuel oil fraction.` The vaporlzed oils pass from the top of the evaporator I5 and are conducted through drying tubes I1, arranged in the converter immediately ahead of the vaporizing tubes I2. During the passage of the vapors through the tubesv I1 the same are dried and entrained liquids removed therefrom for the reason that when the vapors reach the high temperature converting tubes it is important that they should be free of liquid oil in order to prevent carbon formation. Fromv the drying tubes I1, the dry vapors pass through conversion or cracking tubes I8 disposed in the high temperature region ofv the converter Il. The converter may be of any suitable type, but in the form illustrated consists of a setting which is divided internally by a ,transverse bridge wall I9 in the combustion and tube chambers 20 and 2I. The combustion chamber is provided with burners 22 for regulating the temperature of the converter and to control thereby the temperature of the oil or oil vapors passing through the various heating tubes disposed in the converter setting. For example, in the present system of operation, the cracking tubes are heated so that the oil vapors passing therethrough will be raised to a temperature of the order of from 1200" to 1350 F. At this temperature the molecular formation of the gasolines, initially introduced into the process, is subjected to a sufllcient degree oi' rearrangement to change the ordinary hydrocarbons of the paraffin saturated type into hydrocarbons composed largely of olenes and unsaturates, and which latter are known to possess a high anti-knock rating when contained in motor fuels.

From the converter these highly heated vapors pass to the conversion arrester 23 where the highly heated cracked vapors are shock chilled by direct contact with relatively cool liquid oils having, for example, the boiling range of a gasoil fraction, a suincient amount of such cooling oil is introduced into the arrester to drop the temperature of the vapors abruptly and substantially instantaneously from a conversion temperature in excess of 1000 F. to a fractionating temperature not materially in excess of 600' F.

Following the sudden cooling of the cracked vapors, the latter are removed from the arrester by way of the line 24 and transferred to the lower part of the fractionating tower 5. Simi larly, the oils which remain in the liquid form in the bottom of the arrester 2l are transferred by the line 2Ia to the bottom of the fractionating tower 5. This tower is of usual -construction and operates to eil'ect sharp separation of hydrocar-A bons of relatively different boiling range. The vapors pass upwardly through the tower and are subjected to contact with reflux condensate consisting of higher boiling oils. v'I'he oils which remain in vaporous form after passing through the tower and over the reflux coil I are discharged through a pipe line 25 connected with the top of the tower, and lead to a condenser 28 in which the vapors are reduced to liquid form and to permit of the separation of water. if steam is used in the process, and fixed gas from the desired condensate. The latter collects inthe tank 21 as a finished motor fuel distillate.

since gasoline is used as the charging stock. the re-cycle ratio in this system of operation is low. However, the high boiling liquid oils which are removed from the bottom of the tower l by .way of the pipe line 2l consist principally of .fractions having the boiling range of gas-oil.

This high boiling oil is delivered to a pump 2l and thence forced'through'a line Il and a cooler 2| to a gas-oil tank I2. vFrom the gas-oil tank this heavy oil is removed by means of the line 33 and passed through a pump M, and from .the discharge side of the pump u the oil is forced through a pipe line 2l to the liquid oil inlet nozzle 36 of the arrester 22, where such liquid oil of high boiling range is used to shock chill the cracked vapors discharged from the converter".

If desired, the pipe line 25 may be equipped with a valve 26 adjacent to a branch line I1 which is also provided with a valve 28 and which communicates with the pipe line I Ia leading to the vaporizing tubes i2. In this operation a certain amount of excess gas-oil will accumulatein the bottom of the fractionating tower 5, since the heavy ends created by cracking the gasoline will also collect in said tower. Therefore, in order to keep the level of the gas-oil in the working tank 32 constant, it may be necessary to by-pass a small quantity of the gas-oil continuously or intermittently through theivalve 38, meeting at that point the gasoline being pumped by the pump I I, in order to vaporize this gas-oil in the tubes I2 and to thereby pass the gas-oil vapors. along with the gasoline vapors, through the converter, removing the fuel oil present from the bottom of the evaporator Il through the line I l. It will thus be seen that the present invention provides a gas-oil circulating ring in which the arrester 22, forms a part, whereby high boiling oil may be employed for shock chilling the cracked vapors. Excess gas-oil is passed through the converter, together with the gasoline vapors and subjected to cracking reactions.

By removing the lighter ends of the charging stock before cracking, I avoid high permanent gas losses and reduce to a minimum the formation of such gas in the cracking zone. Byv this process I am enabled to transform straight run gasolines of low anti-knock rating into motor fuels of high anti-knock rating.

While I have described a preferred method for carrying out the present invention-and have dwelt in detail on the character of the charging stock, temperature and other operating conditions, nevertheless it will be understood that I do not limit the present invention to the single operation described, but reserve the right to employ all such variations and modifications thereof that may be said to fall fairly within the scope and intent of the invention as expressed in the following claims.

What is claimed is:

l. A non-catalytic process of converting gasolines possessing a low anti-knock rating into motor fuels of higher anti-knock rating, which comprises passing such gasoline through a heated topping zone to remove from the gasoline as vapors low boiling compounds ping abollingv cess of 1000" F., directly contacting the vapors discharged from the cracking zone with a liquid gas-oil fraction whereby to reduce the temperature of the cracked vapors abruptly and substantially instantaneously to a fractionating temperature not in excess of 700 F., then fractionating said vapors to separate the latter into a vaporous fraction possessing the boiling range of ordinary gasoline and the liquid gas-oil fraction, utilizing the self contained heat in the vaporous fraction to effect the topping of the gasoline initially charged to the process by indirect heat interchange therewith, condensing and collecting the vapors released from the .top of the fractionating zone, and passing a portion of the high boiling liquid oils which collect in the bottom of the fractionating zone to the conversion zone.

2. A non-catalytic process of converting gasolines possessing a low anti-knock rating into motor fuels of higher anti-knock rating, which com prises separating such gasoline into a heavy and a light fraction, vaporizing the heavy fraction and passing it through a heated conversion zone wherein the vapors attain a conversion temperature, immediately contacting the products discharged from the conversion zone with a relatively cool oil boiling substantially within the gas oil range whereby to abruptly reduce the ternperature of the cracked vapors to a temperature not in excess of 700 F., fractionating the resulting products to separate -the fraction boiling within the gasoline range from the higher boiling hydrocarbons, effecting the separation of the initial gasoline into light and heavy fractions by indirect heat interchange with the vapors undergoing fractionation, condensing and collecting the vapors released from the top of the fractionating zone, and passing a portion of the high boiling liquid oil which collects in the bottom of the fractionating zone to the conversion zone.

3. A non-catalytic process of converting gasolines possessing a low anti-knock rating into motor fuels of higher anti-knock rating, which comprises separating such gasoline into a heavy and a light fraction, vaporizing the heavy fraction and passing it through a heated conversion zone wherein the vapors attain a conversion temperature, immediately contacting the products discharged from the conversion zone with a relatively cool oil boiling substantially within the gas oil range whereby to abruptly reduce the temperature of the cracked vapors to a temperature below that at which conversion takes place, fractionating the resulting products to separate the fraction boiling Within the gasoline range from the higher boiling hydrocarbons, effecting the separation of the initial gasoline into light and heavy fractions by indirect heat interchange with the vapors undergoing fractionation, conl densing and collecting the vapors released from the top of the fractionating zone, passing high boiling liquid oil from the fractionating zone through a heating and vaporizing section, and passing the resulting vapors to the conversion zone.

CORNELIUS B. WATSON. 

